1. Field of the Invention
The present invention relates to fertilizers. More particularly, the present invention relates to methods and apparatus for coating fertilizer in pellet form to impart time-release characteristics and the resulting coated pellet product.
2. Description of Related Art
Many attempts to provide a fertilizer product having a coating which provides for slow release of the fertilizer, rendering the fertilizer application effective over a long period of time, have been made. Many such processes suffer from sticky buildup in the coating equipment, leading to costly shutdown and cleaning of the apparatus. The products of the past lack sufficient abrasion resistance during handling, thus reducing the slow release properties of the fertilizer product. Prior colored coatings fall short in brightness and brilliance of desired colors for identification and marketability. It is desirable to provide a coated fertilizer product and process for coating resulting in improved abrasion resistance during handling while avoiding sticky buildup in the coating equipment. It is also desirable to provide these products in a selection of colors to improve identification and marketability. It would be desirable to provide for superior hydrophobic qualities to those demonstrated in prior products. It is desirable to provide a coated fertilizer which will not pollute the soil with undesirable chemical residues. It is desirable to provide a coated fertilizer which eliminates odor and dust during application to the soil. It is also desirable to provide an improved apparatus which is optimal to carry out the coating of fertilizer to obtain the desired coated product.
U.S. Pat. No. 3,264,089, issued Aug. 2, 1966, to Hanson, describes a method of making a slow release fertilizer granule product with a urethane resin coating.
U.S. Pat. No. 5,454,851, issued Oct. 3, 1995, to Zlotnikov et al., describes a method of making a slow release fertilizer product having an encapsulating, waterproofing sulfurated coating. Soybean oil may be used as a starting material therefor.
U.S. Pat. No. 5,538,531, issued Jul. 23, 1996, to Hudson et al. describes a method of making a controlled release fertilizer product of a polyisocyanate, a polyol having about the range of 2-6 hydroxyl moieties, and at least one alkyl moiety.
U.S. Pat. No. 4,711,659, issued Dec. 8, 1984, to Moore, describes a method of making a controlled release fertilizer product employing a polyisocyanate and a polyol separately sequentially applied along with a triethanolamine catalyst to form a urethane coating. The addition of fillers is contemplated.
U.S. Pat. No. 5,547,486, issued Aug. 20, 1996, to Detrick et al., describes an apparatus and mode of operation for sequential coating of fertilizer wherein a coating drum includes a plurality of sequential coating stations, each station having a single spray nozzle, for sequentially coating a batch of fertilizer moving through the drum with a plurality of coatings.
U.S. Pat. No. 6,152,981, issued Nov. 28, 2000, to Markusch et al. describes an isocyanate composition for coating fertilizer pellets. The class of coating compositions of the Markusch group of compounds all contains sulfur as a significant component.
U.S. Pat. No. 6,322,606 B1, issued Nov. 27, 2001, to Komoriya et al., describes a coated granular fertilizer having a film of polyurethane resin prepared by a method which includes the steps of (a) reacting an aromatic polyisocyanate with a first polyol component (i.e., castor oil or a castor oil derivative), to obtain a pre-polymer, and (b) reacting the pre-polymer with a second polyol component (i.e., castor oil or its derivative) and a third polyol which is an amine. Aqueous fluid-absorbing particles may be added to the composition.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.